Diesel fuel differentially affects hyphal healing in Gigaspora sp. and Rhizophagus irregularis.

Hydrocarbon pollution is an increasing problem affecting soil ecosystems. However, some microorganisms can cope with these pollutants and even facilitate plant establishment and thus phytoremediation. Within soil, arbuscular mycorrhizal fungi (AMF) have developed several strategies to survive and flourish under adverse conditions. Among these is the hyphal healing mechanism (HHM), a process allowing hyphae to re-establish integrity after physical injury. This mechanism differs among species and genera of AMF. However, whether and to what extent hydrocarbon pollution impacts the HHM is unknown. Here, the HHM was monitored in vitro on two AMF strains, Rhizophagus irregularis MUCL 41833 and Gigaspora sp. MUCL 52331, under increasing concentrations of diesel (1, 2, and 5% v:v). The addition of diesel slowed-down the HHM in both fungi. On Gigaspora sp., this effect was limited and most hyphae were able to heal after injury. Conversely, all steps of healing were severely impaired in R. irregularis. That fungus reconnected the injured hyphae at a much lower frequency than the Gigaspora sp., instead investing its energy to link neighboring hyphae or roots, or developing new branches from uninjured hyphae.

Fungicides With Contrasting Mode of Action Differentially Affect Hyphal Healing Mechanism in Gigaspora sp. and Rhizophagus irregularis.

Fungicides are widely used in conventional agriculture to control fungal diseases, but may also affect non-target microorganisms such as arbuscular mycorrhizal (AM) fungi. These root symbionts develop extended mycelial networks within the soil via mechanisms such as anastomosis that indistinctly concerns intact and damaged hyphae, the latter being named hyphal healing mechanism (HHM). The HHM differs between Glomeraceae and Gigasporaceae. However, the effects of fungicides on this mechanism in unknown. Here, the impact of azoxystrobin, pencycuron, flutolanil, and fenpropimorph at 0.02 and 2 mg L-1 were tested in vitro on the HHM of Gigaspora sp. MUCL 52331 and Rhizophagus irregularis MUCL 41833, and repair events visualized carefully under a dissecting bright-field light microscope. Azoxystrobin was the more detrimental for both AM fungi at 2 mg L-1, while fenpropimorph impacted only R. irregularis (stimulating at low and inhibiting at high concentration). Conversely, flutolanil and pencycuron did not impact any of the two AM fungi. The mechanisms involved remains to be elucidated, but perturbation in the still-to-be firmly demonstrated spitzenkörper or in sterols content as well as a process of hormesis are possible avenues that deserve to be explored in view of a rationale management of chemicals to control fungal pathogens without harming the beneficial AM fungi.

Estimation and identification issues in the promotion time cure model when the same covariates influence long- and short-term survival.

The promotion time cure model is a survival model acknowledging that an unidentified proportion of subjects will never experience the event of interest whatever the duration of the follow-up. We focus our interest on the challenges raised by the strong posterior correlation between some of the regression parameters when the same covariates influence long- and short-term survival. Then, the regression parameters of shared covariates are strongly correlated with, in addition, identification issues when the maximum follow-up duration is insufficiently long to identify the cured fraction. We investigate how, despite this, plausible values for these parameters can be obtained in a computationally efficient way. The theoretical properties of our strategy will be investigated by simulation and illustrated on clinical data. Practical recommendations will also be made for the analysis of survival data known to include an unidentified cured fraction.

Binge drinking is associated with reduced quality of life in young students: A pan-European study.

BACKGROUND: Binge drinking (BD) is frequently observed in youth, with psychological and cognitive consequences, but its link with quality of life has been scarcely explored. METHODS: Sociodemographic and alcohol consumption characteristics were collected in a cross-sectional survey including 15,020 European students. Health-related quality of life was assessed using the Alcohol Quality of Life Scale (AQoLS) measuring the self-reported negative impact of alcohol consumption. A flexible link function, using Bayesian P-splines, was used to study the relationship between alcohol-related quality of life and alcohol consumption. RESULTS: A non-linear relationship between BD and AQoLS scores was identified, showing that: (1) For students presenting moderate BD pattern, alcohol consumption is related to a robust reduction in quality of life, this link remaining stable for students with more intense BD patterns; (2) BD are not strongly associated with social, personal, and work activities, but are linked to an increase in perceived loss of control over consumption; (3) Harmful or hazardous consumption is also related with a massive decrease in quality of life; (4) The strongest relationship between BD and impacted quality of life is found among males and Eastern European students. CONCLUSIONS: These results demonstrate the importance of measuring the perceived relation between alcohol and quality of life, beyond the classically assessed consequences, as this relation is strong among young students. Prevention programs should take this into account, notably regarding the perceived loss of control over alcohol consumption, which constitutes a key factor for the emergence of severe alcohol-use disorders.